Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: olds442 on November 27, 2013, 09:07:12 PM
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The F4U-1A had a 2 stage 2 speed super charger. However they had 3 supercharger positions, Neutral, Low, and High. Wouldn't that make it a 3 speed super charger? or in Neutral is the second stage disabled?
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From Wikipedia
Two-speed and two-stage superchargers[edit]
In the 1930s, two-speed drives were developed for superchargers. These provided more flexibility for the operation of the aircraft, although they also entailed more complexity of manufacturing and maintenance. The gears connected the supercharger to the engine using a system of hydraulic clutches, which were initially manually engaged or disengaged by the pilot with a control in the cockpit. At low altitudes, the low-speed gear would be used in order to keep the manifold temperatures low. At around 12,000 feet (3,700 m), when the throttle was full forward and the manifold pressure started to drop off, the pilot would retard the throttle and switch to the higher gear, then readjust the throttle to the desired manifold pressure. Later installations automated the gear change according to atmospheric pressure.
Another enhancement was the use of two compressors (also known as stages) in series, such two-stage superchargers were also always two-speed. After the air was compressed in the low-pressure stage, the air flowed through an intercooler radiator where it was cooled before being compressed again by the high-pressure stage and then possibly also aftercooled in another heat exchanger. Two stage compressors provided much improved high altitude performance, as typified by the Rolls-Royce Merlin powered Supermarine Spitfire Mk IX and the North American Mustang. In some two-stage systems, damper doors would be opened or closed by the pilot in order to bypass one stage as needed. Some systems had a cockpit control for opening or closing a damper to the intercooler/aftercooler, providing another way to control temperature. Rolls-Royce Merlin engines had fully automated boost control and all the pilot had to do was advance the throttle, the control system would limit boost as necessary until maximum altitude was reached.
If I am correct to the two speed part is literally the same concept as gears in a car. One speed makes the supercharger spin slower, one faster. The two stage part allows for compressing the air twice, or possibly once if desired. The effect of this is a finer control as opposed to just "slow and fast" So that an engine can receive closer to maximum boost without going over the limit at a wider variety of altitudes. At least I think that is how it works.
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From Wikipedia
Two-speed and two-stage superchargers[edit]
In the 1930s, two-speed drives were developed for superchargers. These provided more flexibility for the operation of the aircraft, although they also entailed more complexity of manufacturing and maintenance. The gears connected the supercharger to the engine using a system of hydraulic clutches, which were initially manually engaged or disengaged by the pilot with a control in the cockpit. At low altitudes, the low-speed gear would be used in order to keep the manifold temperatures low. At around 12,000 feet (3,700 m), when the throttle was full forward and the manifold pressure started to drop off, the pilot would retard the throttle and switch to the higher gear, then readjust the throttle to the desired manifold pressure. Later installations automated the gear change according to atmospheric pressure.
Another enhancement was the use of two compressors (also known as stages) in series, such two-stage superchargers were also always two-speed. After the air was compressed in the low-pressure stage, the air flowed through an intercooler radiator where it was cooled before being compressed again by the high-pressure stage and then possibly also aftercooled in another heat exchanger. Two stage compressors provided much improved high altitude performance, as typified by the Rolls-Royce Merlin powered Supermarine Spitfire Mk IX and the North American Mustang. In some two-stage systems, damper doors would be opened or closed by the pilot in order to bypass one stage as needed. Some systems had a cockpit control for opening or closing a damper to the intercooler/aftercooler, providing another way to control temperature. Rolls-Royce Merlin engines had fully automated boost control and all the pilot had to do was advance the throttle, the control system would limit boost as necessary until maximum altitude was reached.
If I am correct to the two speed part is literally the same concept as gears in a car. One speed makes the supercharger spin slower, one faster. The two stage part allows for compressing the air twice, or possibly once if desired. The effect of this is a finer control as opposed to just "slow and fast" So that an engine can receive closer to maximum boost without going over the limit at a wider variety of altitudes. At least I think that is how it works.
I understand how speeds and stages work in superchargers...
What im asking is that in the F4U-1A with the R2800-8W engine the supercharger is a 2 speed supercharger yet has 3 settings, Neutral, Low, and High. Now there is SOME type of forced induction going on even in the neutral position as the engine pulls 49 MAP @ SL. With out some type of forced induction (super charger or turbo charging) it would be around barometric (about 29.9in MAP at SL). Give or take a inch. Now the this proves that even the the Neutral blower position their is still forced induction. There is clearly no turbo in the F4U-1A so this leads my to think that ONLY the 2nd stage is being controlled by the gearing. So that the 1st stage (after the carb) is ALWAYS in a constant RATIO to the engine RPM. The 2nd stage is controlled by this gearing. So at take off power at SL ONLY the 1st stage is active (as it always is) and the 2nd stage is not active (due to Neutral gear selected). Then at 7k as stated in the F4U-1A datasheet the pilot engages the LOW gear and the 2nd stage starts up in LOW. Then at 15k the pilot engages HIGH speed.
Is this correct experts on the F4U?
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I'm not an expert but I believe that's correct. Neutral doesn't use the auxiliary blower. Pilot's manual says to use neutral as long as you get the power you need.
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Neutral is not a "speed"..High and Low are, hence "2" speed. :aok
NOT
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F4U had a ram air system useful up to 5k.
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When it comes to controlling almost anything like auto adjusting doors and such, most switch controls would be of the 3-position type, (Hand-Off-Auto, On-Off-Auto, or Open-Closed-Auto).
The "Auto" selection would normally self-regulate a system and alleviate the pilot from having to constantly monitor this feature. The other non-Auto selections would allow for manual control override. The manual options would be for failure backup operation and maintenance.
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Olds, Check this link out http://books.google.com/books?id=tC22hsLZs9IC&pg=PA7&lpg=PA7&dq=f4u+supercharger&source=bl&ots=U5vK9rCX57&sig=h2o0Oa8uNZZpUwG5KtECtc1aR2U&hl=en&sa=X&ei=ODSmUq_1GtS_kQeyoIGoBw&ved=0CH4Q6AEwCQ#v=onepage&q=f4u%20supercharger&f=false (http://books.google.com/books?id=tC22hsLZs9IC&pg=PA7&lpg=PA7&dq=f4u+supercharger&source=bl&ots=U5vK9rCX57&sig=h2o0Oa8uNZZpUwG5KtECtc1aR2U&hl=en&sa=X&ei=ODSmUq_1GtS_kQeyoIGoBw&ved=0CH4Q6AEwCQ#v=onepage&q=f4u%20supercharger&f=false)
The way I read this is there are basically two superchargers stacked one on the other (two stage). One works all the time, the other works when the control lever is in Low or high (two speed), it's know as the axillary super charger. In reality it's technically a 3 speed with speed 1 operating all the time I guess they didn't count it as a "speed".